Semiconductor display device

ABSTRACT

It is an object of the present invention to provide a semiconductor display device having an interlayer insulating film which can obtain planarity of a surface while controlling film formation time, can control treatment time of heating treatment with an object of removing moisture, and can prevent moisture in the interlayer insulating film from being discharged to a film or an electrode adjacent to the interlayer insulating film. An inorganic insulating film containing nitrogen, which is less likely to transmit moisture compared with an organic resin, is formed so as to cover a TFT. Next, an organic resin film containing photosensitive acrylic resin is applied to the organic insulting film, and the organic resin film is partially exposed to light to be opened. Thereafter, an inorganic insulting film containing nitrogen, which is less likely to transmit moisture compared with an organic resin, is formed so as to cover the opened organic resin film. Then, in the opening part of the organic resin film, a gate insulating film and the two layer inorganic insulating film containing nitrogen are opened partially by etching to expose an active layer of the TFT.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor display device in whichan organic resin film is used as an interlayer insulating film.

2. Description of the Related Art

In recent years, a technology for forming a TFT on a substrate hasachieved a great advance, and application of the technology to an activematrix semiconductor display device which is one of semiconductordevices has been in progress. In particular, a TFT using apolycrystalline semiconductor film can operate at a high speed becauseit has field effect mobility higher than that of a conventional TFTusing an amorphous semiconductor film. Thus, it is possible to performcontrol of pixels, which has been conventionally performed by a drivecircuit provided outside a substrate, with a drive circuit formed on asubstrate identical with a substrate on which the pixels are formed.

A TFT includes an active layer, which is obtained by adding impuritiesgiving one conductive type to a semiconductor film, a gate electrode,and a gate insulating film provided between the active layer and thegate electrode. Further, in general, an interlayer insulating filmincluding an insulating film is formed covering the TFT, and a wiring tobe electrically connected to the TFT is formed on the interlayerinsulating film.

Unless a surface of the interlayer insulating film is sufficientlyplanarized, when the wiring to be electrically connected to the TFT isformed on the interlayer insulating film, disconnection of the wiring iscaused or the wiring becomes partially thin to increase a wiringresistance. In addition, in the case in which a pixel electrode isformed on the interlayer insulating film, unevenness is formed on asurface of the pixel electrode due to unevenness of a surface of theinterlayer insulating film or a thickness of the pixel electrode cannotbe uniformalized, which appears as irregularity in display.

Therefore, it is necessary to form the interlayer insulating filmsufficiently thick, for example, approximately 1 to 5 μm in order toprevent unevenness from appearing on the surface of the interlayerinsulating film according to a shape peculiar to the TFT.

The interlayer insulating films are roughly classified into an inorganicinsulating film hereinafter referred to as inorganic resin-film and aninsulating, film including an organic resin having an insulatingproperty (hereinafter referred to as organic resin film).

The inorganic insulating film is formed by chemical vapor depositionsuch as the CVD method or the sputtering method. Thus, in the case inwhich the inorganic insulating film is used as an interlayer insulatingfilm, there is a disadvantage that treatment takes time because theinorganic insulating film has to be formed thick enough to allow asurface thereof to be planarized.

On the other hand, in the case in which the organic resin film is used,since an organic resin can be applied to a substrate on which a TFT isformed, an interlayer insulating film with a surface thereof planarizedcan be formed easily.

Incidentally, a wiring to be connected to a TFT is formed by forming afilm having conductivity (hereinafter referred to a conductive film) onan interlayer insulating film in which a contact hole is opened andetching the conducive film.

In this case, both wet etching and dry etching can be used as theetching of the conductive film. However, the wet etching cannot copewith micronization of a wiring pattern of 3 μm or less because it isisotropic etching. On the other hand, the dry etching is capable ofcoping with micronization of a wiring pattern because anisotropicetching is possible with the dry etching.

However, a problem of the dry etching is that, when a conductive film onan interlayer insulating film including an organic resin film, a surfaceof the organic resin film is roughened. If the surface of the organicresin film is roughened, planarity of a surface of a pixel electrode tobe formed on the organic resin film is spoiled, which affects display ofa pixel.

In addition, organic resin is high in a water absorbing property andabsorbs moisture in alkaline water solution, which is used indevelopment, to swell. Thus, it is necessary to provide a step forsubjecting the organic resin film to heating treatment after developmentto evaporate moisture contained therein. Moreover, even if the organicresin film is subjected to the heating treatment to evaporate themoisture, it is likely that the film absorbs moisture in an adjacentfilm or the atmosphere, the moisture in the film corrodes a wiringformed in contact with the organic resin film as time elapses, andlong-term reliability of a panel is spoiled.

SUMMARY OF THE INVENTION

The present invention has been devised in view of the above and otherdrawbacks, and it is an object of the present invention to provide asemiconductor display device having an interlayer insulating film whichcan obtain planarity of a surface of the interlayer insulating filmwhile controlling film formation time, can control time for heatingtreatment for removing moisture in the interlayer insulating film, andcan prevent the moisture from being discharged to a film or an electrodeadjacent to the interlayer insulating film.

In addition, since a circuit comprising a thin film transistor more orless has unevenness on its surface, it has been a general practice toplanarize the surface with an organic resin film or the like in forminga liquid crystal element or a light emitting element thereon. However,facts described below have been proven by researches of the applicant.That is, it has been proved that, in the case in which a resin film isused as an interlayer insulating film and a contact hole is formed usinga dry etching technique, a threshold voltage (Vth) of a completed thinfilm transistor fluctuate largely. For example, data shown in FIGS. 24Aand 24B is a result of examining fluctuation of threshold voltages of athin film transistor formed on an SOI substrate. Black circles in thefigure indicate the case in which a laminated structure of a siliconnitride (SiN) film and an acrylic film is used as the interlayerinsulating film and white triangles in the figure indicate the case inwhich a laminated structure of a silicon nitride oxide (SiNO) film and asilicon oxide nitride (SiON) film is used as the interlayer insulatingfilm. In addition, in both the cases, the dry etching technique is usedin an opening of the contact hole. Note that, “SiNO” and “SiON” aredistinguished to mean that the former contains more nitrogen than oxygenand the latter contains more oxygen than nitrogen.

The data of FIGS. 24A and 24B is a graph in which the fluctuation ofthreshold voltages according to statistic processing, and a channellength (length of carrier movement) is represented by the horizontalaxis and Vth fluctuation is represented by the vertical axis. “Quartiledeviation” is known as statistic processing. The quartile deviation is adifference between a value of 25% and a value of 75% in a normalprobability graph and is attracting attention as statistic processingwhich is not affected by an abnormal value. The applicant defines adifference between a value of 16% and a value of 84% as 16-percentiledeviation based upon this quartile deviation (also referred to as25-percentile deviation), and plots the value on the vertical axis as“Vth deviation”. Note that, since the 16-percentile deviation isequivalent to ±σ in terms of a normal probability distribution, valuesmultiplied by a coefficient, respectively, and changed to values whichcan be regarded as ±3σ are used in data plot. Judging only from thedata, an n-channel TFT and a p-channel TFT which use the acrylic film asthe interlayer insulating layer have fluctuation approximately fourtimes and twice as large as fluctuation of those using the SiNO film andthe SiON film as the interlayer insulating layer, respectively. It isclear that fluctuation is larger when the acrylic film is used. Theapplicant surmises that plasma damage at the time of the dry etchingcauses the acrylic film to capture charges, which results in fluctuationof threshold voltages.

The present invention has been devised in view of the above-describedproblems, and it is an object of the present invention to provide atechnique for manufacturing a thin film transistor without fluctuating athreshold voltage thereof in manufacturing a display device using anorganic resin film as interlayer insulating film to thereby attainingimprovement of stability of an operation performance of the displaydevice and increase in a design margin in circuit design. In addition,it is another object of the present invention to attain improvement ofimage quality of the display device.

In the present invention, the perimeter of an organic resin filmcontaining a positive photosensitive acrylic resin is surrounded by aninsulating film containing nitrogen which is less likely to transmitmoisture compared with an organic resin.

More specifically, after forming a TFT, an inorganic insulating filmcontaining nitrogen, which is less likely to transmit moisture comparedwith organic rein, is formed so as to cover the TFT. Next, an organicresin containing a photosensitive acrylic resin is applied to theinorganic insulating film to form an organic resin film. The organicresin film is partially exposed to light to open the same. Thereafter,an inorganic insulating film containing nitrogen which is less likely totransmit moisture compared with an organic resin is formed so as tocover the opened organic resin film. Then, in the opening part of theorganic resin film, a gate insulating film and the two-layer inorganicinsulating films containing nitrogen are etched to partially open themto expose an active layer of the TFT.

In this etching, it is essential to prevent the organic resin film frombeing exposed in a region where a part, in which it is desirable toavoid influence of moisture and influence of unevenness of a surface ofa film, such as a wiring or a pixel electrode is formed on the surfacein a later process. In addition, the other regions may be completelycovered by the inorganic insulating film.

In general, since the inorganic insulating film has less etching damagedue to dry etching compared with the organic resin film represented byan acrylic resin, roughness of a surface of the film is less. Thus,since unevenness is prevented from appearing on a surface of a pixelelectrode or the like to be formed later or a thickness of the pixelelectrode is prevented from becoming non-uniform, irregularity can beprevented from occurring in display.

In addition, since the organic resin film is covered by the inorganicinsulting film containing nitrogen which is less likely to transmitmoisture compared with the organic resin, discharge of moisture from theorganic resin film can be controlled and, conversely, the organic resinfilm can be prevented from absorbing alkaline water solution, which isused in development, to swell, and time for heating treatment for thepurpose of removing moisture after the development can be controlled.Thus, discharge of moisture in the organic resin film to an adjacentfilm or electrode can be prevented more and long-term reliability of apanel can be improved. Moreover, in the case in which a light emittingelement represented by an organic light emitting diode (OLED) is used,luminance of the light emitting element can be prevented fromdeteriorating due to moisture discharged from the organic resin film.

Note that, in the present invention, a photosensitive acrylic resin isused as the organic resin film. The photosensitive organic resinincludes a positive photosensitive organic resin in which a part exposedto an energy beam such as light; electron, or ion is removed and anegative photosensitive organic resin in which an exposed part remains.FIGS. 1A to 1D show sectional views of an opening part of the positiveacrylic resin and an opening part of the negative acrylic resin.

In the case of the positive acrylic resin, as shown in FIG. 1A, after afirst inorganic insulating film 7000 is formed, a positive acrylicorganic resin film is formed and a part to be opened of the organicresin film is exposed to light. Thereafter, the part exposed to light isremoved by development to expose the first inorganic insulating film7000. Then, a second inorganic insulating film 7002 is formed so as tocover a positive organic resin film 7001 on which the opening part isformed and the exposed part of the first inorganic insulating film 7000.

FIG. 1B shows an enlarged view of a section of the opened positiveorganic resin film 7001. As shown in FIG. 1B, the section of the openingpart curves, and an inclination of a tangent line in each part on thesurface of the positive organic resin film 7001 with respect to asubstrate direction (horizontal direction) is smaller as the part isfarther apart from the opening part. In other words, a curvature radiusat respective contact points R1, R2, and R3 increases continuously asthe point is farther apart from the opening part and draws a parabola.Then, curvature centers of all the contact points R1, R2, and R3 existon the positive organic resin film 7001 side (substrate side).

In the case in which the positive acrylic resin is used, an angle 8 of atangent line with respect to the substrate at a contact point in a partin the opening part where the positive organic resin film 7001 breakscan be set to 30° or more and 65° or less.

In this way, in the case of the positive organic resin film, all thecurvature centers on the surface of the organic resin film in theopening part exist on the substrate side, and a part of the film is lesslikely to remain in a part, which is desired to be opened, due toetching failure. Thus, contact failure is less likely to occur, whichleads to increase in yield.

In the case of the negative acrylic resin, as shown in FIG. 1C, after afirst inorganic insulating film 7005 is formed, a negative acrylicorganic resin film is formed, and parts other than a part to be openedof the organic resin film is exposed to light. Thereafter, the part notexposed to light is removed by development to expose the first inorganicinsulating film 7005. Then, a second inorganic insulating film 7007 isformed so as to cover a negative organic resin film 7006 in which theopening part is formed and the exposed part of the first inorganicinsulating film 7005.

FIG. 1D shows an enlarged view of a section of the opened negativeorganic resin film 7006. As shown in FIG. 1D, the section of the openingpart curves, and an inclination of a tangent line in each part on thesurface of the negative organic resin film 7006 with respect to asubstrate direction (horizontal direction) is smaller as the part isfarther apart from a contact point R0 of the opening part toward theoutside of the opening part. In other words, a curvature radius atrespective contact points R1, R2, and R3 increases continuously as thepoint is farther apart from the contact point R0 toward the outside ofthe opening part. For example, in the case of the positivephotosensitive acrylic resin, although depending upon conditions ofexposure to light, a minimum curvature radius is approximately 3 to 30μm at an end part thereof. The inclination of the tangent line decreasestoward the center of the opening part from the contact point R0, and thecurvature radius also continuously increases. Then, curvature centers ofall the contact points R1, R2, and R3 located on the outside of theopening part from the contact point R0 exist on the negative organicresin film 7006 side (substrate side). A curvature center of a contactpoint R-1 located on the center side of the opening part from thecontact point R0 exists on the opposite side of the negative organicresin film 7006 (opposite side of the substrate).

As described above, in the case of the negative organic resin film, thecurvature center on the surface of the organic resin film in the openingpart exists on the opposite side of the substrate from the contact pointR0 toward the center. The longer a distance from the contact point R0 toa part where the negative organic resin film 7006 breaks, the smaller anarea of the opening part becomes and more likely contact failure iscaused. This distance changes depending upon conditions of etching or athickness of the organic resin film before being opened. In addition,although FIGS. 1A to 1D are illustrated with the case of the acrylicresin as an example, in the case in which an organic resin film otherthan the acrylic organic resin film is used, the distance from thecontact point R0 to the part where the organic resin film breaks alsochanges depending upon a composition of the resin. Thus, even in thecase in which the negative photosensitive organic resin is used to formthe sectional shape shown in FIGS. 1C and 1D, it is possible to use thenegative photosensitive organic resin if the distance from the contactpoint R0 to the part where the negative organic resin film 7006 breakscan be reduced to a degree for allowing the area of the opening part tobe secured sufficiently.

However, the organic resin which can form the sectional shape shown inFIGS. 1A and 1B is still preferable to the organic resin which forms thesectional shape shown in FIGS. 1C and 1D as a resin to be used as a partof an interlayer insulating film. However, all positive photosensitiveorganic resins cannot always form the sectional shape shown in FIGS. 1Aand 1B. Although positive acrylic can form the sectional shape shown inFIGS. 1A and 1B, positive polyimide cannot form the sectional shape.

In addition, in the case in which non-photosensitive organic resin isused, general dry etching is used for forming an opening in aninterlayer insulating film. The dry etching is an etching method usingan active radical or plasma of a reactive gas. Since the interlayerinsulating film has a thickness ten times as large as that of a gateinsulating film, the dry etching with an object of forming an openingtakes time. When a substrate on which a TFT is formed is exposed toplasma for a long time, threshold values of the TFT are likely tofluctuate to a positive side due to so-called charging damage in which ahole is trapped in the gate insulating film. Thus, by using thephotosensitive organic resin to form an opening with the wet etching asin the present invention, time required for the dry etching can bereduced significantly and fluctuation of threshold value of the TFT canbe controlled.

Further, in the present invention, a gate electrode of a TFT and anelectrode of a capacitor used in a drive circuit of a semiconductordisplay device are simultaneously formed, and a wiring to beelectrically connected to the TFT and the other electrode of thecapacitor are simultaneously formed. Then, in an opening part of anorganic resin film, two-layer inorganic insulating films overlap eachother with the two electrodes between them, whereby a storage capacitoris formed.

Since the semiconductor display device has its drive circuit formed on aglass substrate, the number of pins of an FPC can be reduced, physicalimpact resistance can be increased, and a size of the semiconductordisplay device itself can be controlled. In addition, decrease in yielddue to connection failure of the FPC can be controlled.

Note that, representative examples of the drive circuit include ascanning line drive circuit for selecting one or several pixels amongplural pixels, which are provide in a pixel portion, in order and asignal line drive circuit for inputting a signal having imageinformation (video signal) in the selected pixel(s). Both the pixels canbe formed using the present invention. In particular, it is possible touse a capacitor to be formed using the present invention, for example,as a capacitor included in a capacity division type D/A conversioncircuit of the signal line drive circuit.

In addition, it is also possible to form other semiconductor devicesused in a semiconductor display device such as a controller or a CPU,which have been formed on a silicon substrate, integrally on a glasssubstrate using the present invention. In particular, a capacitor to bemanufactured using the capacitor of the present invention can be used asa capacitor included in every circuit such as a booster circuit, aDynamic Random Access Memory (DRAM), an analog latch, a capacitydivision type D/A conversion circuit, and a protection circuit forcoping with static electricity.

By integrally forming other circuits used in a semiconductor displaydevice such as a controller and a CPU on a glass substrate, the numberof pins of an FPC can be further reduced, physical impact resistance canbe increased, and a size of the semiconductor display device itself canbe controlled. In addition, decrease in yield due to connection failureof the FPC can be further controlled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D are sectional views of a photosensitive acrylic film inan opening part;

FIG. 2 is a sectional view of a photosensitive positive polyimide filmin an opening part;

FIGS. 3A to 3C are sectional views of a contact hole;

FIGS. 4A to 4D are views showing a positional relationship between thecontact hole and a wiring;

FIGS. 5A and 5B are sectional views of a TFT and a storage capacitorincluded in a semiconductor display device of the present invention;

FIGS. 6A and 6B are a block diagram and a circuit diagram of a drivecircuit of the semiconductor display device of the present invention,respectively;

FIGS. 7A and 7B are a mask diagram and a circuit diagram of a boostercircuit, respectively;

FIGS. 8A to 8C are views showing a manufacturing method of thesemiconductor display device of the present invention;

FIGS. 9A to 9C are views showing the manufacturing method of thesemiconductor display device of the present invention;

FIGS. 10A to 10C are views showing the manufacturing method of thesemiconductor display device of the present invention;

FIGS. 11A to 11C are views showing the manufacturing method of thesemiconductor display device of the present invention;

FIGS. 12A and 12B are views showing the manufacturing method of thesemiconductor display device of the present invention;

FIGS. 13A to 13D are sectional views of the semiconductor display deviceof the present invention;

FIGS. 14A and 14B are sectional views of the semiconductor displaydevice of the present invention;

FIGS. 15A and 15B are views showing the manufacturing method of thesemiconductor display device of the present invention;

FIG. 16 is a plan view of the semiconductor display device of thepresent invention;

FIG. 17 is a block diagram showing a structure of a controller of alight emitting device;

FIG. 18 is a sectional view of a semiconductor display device of thepresent invention;

FIGS. 19A and 19B are a block diagram and a circuit diagram of a drivecircuit of the semiconductor display device of the present invention,respectively;

FIGS. 20A and 20B are block diagrams showing structures of a CPU and anASIC included in the semiconductor display device of the presentinvention;

FIG. 21 is a sectional view of a semiconductor display device of thepresent invention;

FIGS. 22A to 22H are views of electronic equipment using thesemiconductor display devices of the present invention;

FIG. 23 is a circuit diagram of a booster circuit included in thesemiconductor display device of the present invention;

FIG. 24 shows graphs representing a channel length and a threshold valueof a TFT;

FIGS. 25A and 25B show graphs representing CV characteristics of theTFT;

FIGS. 26A and 26B are sectional views of a non-photosensitive acrylicfilm in an opening part;

FIGS. 27A and 27B are sectional views of a positive photosensitiveacrylic film in an opening part;

FIGS. 28A and 28B are sectional views of a negative photosensitiveacrylic film in an opening part; and

FIGS. 29A and 29B are sectional views of a positive photosensitivepolyimide film in an opening part.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 shows an enlarged view of a section in an opening part in thecase in which positive photosensitive polyimide is used. As shown inFIG. 2, a positive polyimide film is formed after a first inorganicinsulating film 7010 is formed in the same manner as the case in whichpositive acrylic is used. Then, an opening part is formed by exposing apart to be opened to light and developing the part, whereby the firstinorganic insulating film 7010 is exposed. Then, a second inorganicinsulating film 7012 is formed so as to cover a positive polyimide film7011 in which the opening part is formed and the exposed part of thefirst inorganic insulating film 7010.

Since an end of the positive polyimide film 7011 in which the openingpart is formed is not sufficiently roundish in the opening part, when awiring is formed on the second inorganic insulating film 7012, a filmthickness of the wiring is reduced at the end to increase a wiringresistance. In addition, in the case in which the second inorganicinsulating film 7012 is formed by the chemical vapor deposition method,since the end of the positive polyimide film 7011 in the opening part isnot sufficiently roundish, the second inorganic insulating film 7012 maybe formed thicker at an end 7013 than other parts of the film. This isbecause, when material molecules constituting a thin film adhere to asurface to be formed, the material molecules move on the surface lookingfor a stable site but tend to gather in a part of a shape having anacute angle (shape to be a projected part) like an upper end of acontact hole. This tendency is particularly conspicuous in theevaporation method. If the second inorganic insulating film 7012 isformed thick partially at the end 7013, a film thickness of the wiringis reduced especially at the end to increase the wiring resistance.

Therefore, it is not preferable to use the positive photosensitivepolyimide or other organic resins, which form a sectional shape not incurves at an end of an opening part as shown in FIG. 2, as a part of aninterlayer insulating film of the present invention.

Next, a section in the vicinity of a contact hole at the time when thecontact hole is formed by etching to open an inorganic insulating filmwill be described. After forming films to a state shown in FIG. 1A, aresist mask 7021 is formed and a first inorganic insulating film 7000, asecond inorganic insulating film 7002, and a gate insulating film 7022formed between the first inorganic insulating film 7000 and asemiconductor film are subjected to dry etching to form a contact hole7023 as shown in FIG. 3A.

Note that FIG. 3B shows a state in the vicinity of the contact holeviewed from an upper surface for a substrate. For ease of inspection ofthe drawing, a state after removing the resist mask 7021 is shown. Asection along line A-A′ of FIG. 3B corresponds to FIG. 3A.

The contact hole 7023 is formed inside an opening part 7024 formed inthe positive organic resin film 7001. Then, as shown in FIG. 3C, aconductive film 7025 is formed on the second inorganic insulating film7002 covering the contact hole 7023. Then, the conductive film 7025 ispatterned to form a wiring.

FIGS. 4A to 4D show a positional relationship between the opening part7024 of the positive organic resin film 7001 and the contact hole 7023.FIG. 4A shows a plan view of the vicinity of the contact hole 7023. Notethat FIG. 4B shows a sectional view along line A-A′ of FIGS. 4A to 4D.

A wiring 7026 obtained by patterning the conductive film 7025 isconnected with a semiconductor film 7300 formed under the gateinsulating film 7022 via the contact hole 7023 formed substantially inthe center of the opening part 7024.

In this way, the contact hole 7023 is formed so as to be always settledin the opening part 7024 and is adapted such that the positive organicresin film 7001 is not exposed in the contact hole 7023 due to theformation of the contact hole 7023.

Note that, although the contact hole 7023 is laid out so as to belocated substantially in the center of the opening part 7024 in FIGS. 4Aand 4B, the present invention is not limited to this structure. Thecontact hole 7023 only has to be settled in the opening part 7024 andmay deviate to one direction.

FIG. 4C shows a plan view of the vicinity of the contact hole 7023 inthe case in which the contact hole 7023 deviates to one direction in theopening part 7024. Note that FIG. 4D shows a sectional view along B-B′of FIG. 4C.

The wiring 7026 obtained by patterning the conductive film 7025 isconnected with a semiconductor film (not shown) formed under the gateinsulating film 7022 via the contact hole 7023, which deviates to anupper side direction in the figure, in the opening part 7024.

Next, structures of a TFT and a capacitor in the semiconductor displaydevice of the present invention will be described with reference toFIGS. 5A and 5B.

In FIG. 5A, a TFT 8001 is formed on an insulating surface 8000. The TFT8001 is a top gate type and has a semiconductor film 8002, a gateinsulating film 8003 which is in contact with the semiconductor film8002, and a gate electrode 8004 which is in contact with the gateinsulating film 8003. The semiconductor film 8002 is in contact with theinsulating surface 8000. The semiconductor film 8002 has a channelforming region 8005 and impurity regions 8006 which exist on both sidesof the channel forming region 8005.

On the other hand, a first electrode for capacitor 8007 formed on thegate insulating film 8003 can be formed from the same conductive film asthe gate electrode 8004.

Then, a first inorganic insulating film 8008 is formed so as to coverthe TFT 8001 and the first electrode for capacitor 8007. The firstinorganic insulating film 8008 is an insulating film containing nitrogenand has a characteristic that it is less likely to penetrate moisturethan an organic resin film to be formed later.

Then, after applying a photosensitive organic resin on the firstinorganic insulating film 8008, an organic resin film 8009 having anopened part is formed by baking the photosensitive organic resin andexposing and developing a part desired to be opened. At this point, apart of the first inorganic insulating film 8008 is exposed in theopening part.

Then, a second inorganic insulating film 8010 is formed covering theorganic resin film 8009 and a part of the first inorganic insulatingfilm 8008 exposed in the opening part. Similar to the first inorganicinsulating film 8008, the second inorganic insulating film 8010 is aninsulating film containing nitrogen and has a characteristic that it isless likely to penetrate moisture than an organic resin film.

Note that since the first inorganic insulating film 8008 and the secondinorganic insulating film 8010 are used as dielectric bodies of acapacitor, a capacitance of the capacitor is reduced if the films aretoo thick and treatment time required for film formation cannot becontrolled. On the contrary, if the films are too thin, an effect thatpenetration of moisture is prevented is weakened. The first inorganicinsulating film 8008 and the second inorganic insulating film 8010preferably have a film thickness of approximately 10 nm to 200 nm,respectively, and a total film thickness of the two layers is preferablyapproximately 20 nm to 400 nm.

Then, in the opening part of the organic resin film 8009, the gateinsulating film 8003, the first inorganic insulating film 8008, and thesecond inorganic insulating film 8010 are subjected to dry etching so asto expose a part of the semiconductor film and a contact hole is formed.In this case, the semiconductor film 8002 has an effect as an etchingstopper.

In this case, the first inorganic insulating film 8008 and the secondinorganic insulating film 8010, which exist on the first electrode forcapacitor 8007, are covered by a resist mask so as not to be etched.

Then, the resist mask is removed by a developer. In general, an alkalinewater solution is used as the developer, which contains a large quantityof moisture. In the present invention, since the organic resin film 8009is covered by the first inorganic insulating film 8008 and the secondinorganic insulating film 8010, the organic resin film 8009 is neverexposed to the developer directly. Thus, the moisture of the developeris less likely to enter the organic resin film 8009 and swell.Therefore, after removing the resist mask with the developer, time forheating treatment for the purpose of removing moisture can be reduced.

Then, a conductive film is formed on the second inorganic insulatingfilm 8010 so as to cover the contact hole. Then, a wiring 8011 connectedto the semiconductor film 8002 and the second electrode for capacitor8012 are formed by etching the conductive film. The second electrode forcapacitor 8012 is overlapped the first electrode for capacitor 8007 withthe first inorganic insulating film 8008 and the second inorganicinsulating film 8010 between them. A storage capacitor 8013 is formed ofthe second electrode for capacitor 8012, the first inorganic insulatingfilm 8008, the second inorganic insulating film 8010, and the firstelectrode for capacitor 8007.

The present invention has characteristics in that this storage capacitor8013 is used as a capacitor included in a drive circuit of asemiconductor display device, a CPU, a controller, or other circuits.Note that the TFT 8001 may be a top gate type or a bottom gate type.

Note that, in addition to the storage capacitor of FIG. 5A, a storagecapacitor may be further formed between the semiconductor film and thefirst electrode for capacitor 8007. FIG. 21 shows an example in which afirst storage capacitor 8053 is formed by overlapping a first electrodefor capacitor 8051 and a semiconductor film for capacitor 8050 with eachother with a gate insulating film 8052 between them. In addition,similar to FIG. 5A, the first electrode for capacitor 8051 and thesecond electrode for capacitor 8054 with each other with a firstinorganic insulating film 8055 and a second inorganic insulating film8056 between them, whereby a second storage capacitor 8057 is formed. Inthis way, a capacitance in the same area can be increased by forming thecapacitors one on top of the other.

FIG. 5B shows a structure of the semiconductor device of the presentinvention in the case in which a TFT is a bottom gate.

In FIG. 5B, a TFT 8101 is formed on an insulating surface 8100. The TFT8101 is a bottom gate type and has a semiconductor film 8102, a gateinsulating film 8103 which is in contact with the semiconductor film8102, and a gate electrode 8104 which is in contact with the gateinsulating film 8103. The gate electrode 8104 is in contact with theinsulating surface 8100. The semiconductor film 8102 has a channelforming region 8105 and impurity regions 8106 which exists on both sidesof the channel forming region 8105. In addition, reference numeral 8115denotes an insulating film which is used as a mask when an impurity isadded to the semiconductor film, which is referred to as a channelprotection film in this context.

On the other hand, a first electrode 8107 formed on the insulatingsurface 8100 can be formed from the same conductive film as the gateelectrode 8104.

Then, a first inorganic insulating film 8108 is formed so as to coverthe TFT 8101 and the first electrode for capacitor 8107. Then, afterapplying a photosensitive organic resin on the first inorganicinsulating film 8108, an organic resin film 8109 having an opening partis formed by baking the photosensitive organic resin and exposing anddeveloping a part desired to be opened. At this point, a part of thefirst inorganic insulating film 8108 is exposed in the opening part.

Then, a second inorganic insulating film 8110 is formed covering theorganic resin film 8109 and a part of the first inorganic insulatingfilm 8108 exposed in the opening part. Similar to the first inorganicinsulating film 8108, the second inorganic insulating film 8110 is aninsulating film containing nitrogen and has a characteristic that it isless likely to penetrate moisture than an organic resin film.

Note that since the first inorganic insulating film 8108 and the secondinorganic insulating film 8110 are used as dielectric bodies of acapacitor, a capacitance of the capacitor is reduced if the films aretoo thick and treatment time required for film formation cannot becontrolled. On the contrary, if the films are too thin, an effect thatpenetration of moisture is prevented is weakened. In addition, in thecase of the TFT of the bottom gate type, the gate insulating film 8103also exists between the first electrode for capacitor 8107 and a secondelectrode for capacitor 8112 and is used as a part of the dielectricbody. Thus, it is necessary to determine film thicknesses of the firstinorganic insulating film 8108 and the second inorganic insulating film8110 taking into account a film thickness of the gate insulating film8103. The first inorganic insulating film 8108 and the second inorganicinsulating film 8110 preferably have a film thickness of approximately10 nm to 200 nm, respectively, and a total film thickness of the threelayers including the gate insulating film 8103 is preferablyapproximately 30 nm to 500 nm.

Then, in the opening part of the organic resin film 8109, the gateinsulating film 8103, the first inorganic insulating film 8108, and thesecond inorganic insulating film 8110 are subjected to dry etching so asto expose a part of the semiconductor film and a contact hole is formed.In this case, the semiconductor film 8102 has an effect as an etchingstopper. In addition, the first inorganic insulating film 8108 and thesecond inorganic insulating film 8110, which exist on the firstelectrode for capacitor 8107, are covered by a resist mask so as not tobe etched.

Then, the resist mask is removed by a developer. In general, an alkalinewater solution is used as the developer, which contains a large quantityof moisture. In the present invention, since the organic resin film 8109is covered by the first inorganic insulating film 8108 and the secondinorganic insulating film 8110, the organic resin film 8109 is neverexposed to the developer directly. Thus, the moisture of the developeris less likely to enter the organic resin film 8109 and swell.Therefore, after removing the resist mask with the developer, time forheating treatment for the purpose of removing moisture can be reduced.

Then, a conductive film is formed on the second inorganic insulatingfilm 8110 so as to cover the contact hole. Then, a wiring 8111 connectedto the semiconductor film 8102 and the second electrode for capacitor8112 are formed by etching the conductive film. The second electrode forcapacitor 8112 overlaps the first electrode for capacitor 8107 with thefirst inorganic insulating film 8108 and the second inorganic insulatingfilm 8110 between them. A storage capacitor 8113 is formed of the secondelectrode for capacitor 8112, the first inorganic insulating film 8108,the second inorganic insulating film 8110, and the first electrode forcapacitor 8107.

Next, a structure of a drive circuit of the semiconductor display devicemanufactured using the present invention will be described citing anexample.

FIG. 6A shows a block diagram of the semiconductor display device of thepresent invention. Reference numeral 115 denotes a signal line drivecircuit; 116, a scanning line drive circuit; and 120, a pixel portion.The signal line drive circuit 115 has a shift register circuit 115_1, alevel shift circuit 115_2, and a sampling circuit 115_3. Note that, inFIG. 6A although the level shift circuit 115_2 is provided between theshift register circuit 115_1 and the sampling circuit 115_3, the levelshift circuit 115_2 may be incorporated in the shift register circuit115_1.

In addition, reference numeral 121 denotes a booster circuit, which cangenerate a power supply voltage of various levels, which is supplied toa drive circuit, from a supplied power supply voltage.

When a clock signal (CLK) and a start pulse signal (SP) are supplied tothe shift register circuit 115_1, the shift register circuit 115_1generates a timing signal for controlling timing for sampling a videosignal.

The generated timing signal is supplied to the level shift circuit115_2. On the other hand, the power supply voltage generated in thebooster circuit 121 has been supplied to the level shift circuit 115_2,and the level shift circuit 115_2 amplifies an amplitude of a voltage ofthe timing signal using the supplied power supply voltage.

The timing signal amplified in the level shift circuit 115_2 is inputtedin the sampling circuit 115_3. Then, the video signal inputted in thesampling circuit 115_3 is sampled synchronizing with the timing signalinputted in the sampling circuit 115_3 and is inputted in the pixelportion 120 via the signal line.

FIG. 6B shows an example of a circuit diagram of the booster circuit121. The booster circuit shown in FIG. 6B has two n-channel TFTs 122 and123 and two storage capacitors 124 and 125. Note that the boostercircuit shown here is only an example, and the present invention is notlimited to this booster circuit.

A power supply voltage Vdd is supplied to both of a gate and a drain ofthe n-channel 122. Note that Vdd>Gnd. In addition, both of the gate andthe drain of the n-channel TFT 123 are connected to a source of then-channel TFT 122. One of two electrodes for capacitor included in thecapacitor 124 is connected to the source of the n-channel TFT 122, andthe clock signal CLK is supplied to the other of the two electrodes. Inaddition, one of two electrodes for capacitor included in the capacitor125 is connected to a source of the n-channel TFT 123 and the other isconnected to a Gnd. A voltage of the source of the n-channel TFT 123 issupplied to the level shift circuit 115_2 as a power supply voltage.

FIG. 7A shows a plan view of the booster circuit shown in FIG. 6B. Notethat a sectional view along A-A′ of FIG. 7A corresponds to FIG. 7B.

The n-channel TFT 123 has a semiconductor film 124, a gate insulatingfilm 125, and a gate electrode 126. Further, the n-channel 123 iscovered by a first inorganic insulating film 128. In addition, anorganic resin film 129 having an opening part is formed on the firstinorganic insulating film 128, and a second inorganic insulating film130 is formed covering the organic resin film 129.

A wiring 127 is connected to the gate electrode 126 and thesemiconductor film 124 in the opening part of the organic resin film 129via contact holes formed in the gate insulating film 125, the firstinorganic insulating film 128, and the second inorganic insulating film130. In addition, the wiring 131 is connected to the semiconductor film124 in the opening part of the organic resin film 129 via the contactholes formed in the gate insulating film 125, the first inorganicinsulating film 128, and the second inorganic insulating film 130.

In addition, a first electrode for capacitor 133 overlaps a secondelectrode for capacitor, which is a part of the wiring 131, sandwichingthe first inorganic insulating film 128 and the second inorganicinsulating film 130 between them in the opening part of the organicresin film 129, whereby a storage capacitor 134 is formed.

Note that the booster circuit included in the semiconductor device ofthe present invention is not limited to this structure. FIG. 23 shows abooster circuit having a structure different from that of the boostercircuit shown in FIG. 6B. In the booster circuit shown in FIG. 13 threeTFTs correspond to one capacitor, and the number of capacitors and thenumber of TFT can be increased in accordance with a value of apredetermined voltage with a capacitor and three TFTs corresponding tothe capacitor as one unit. In FIG. 23, TFTs SW1 to SW9 are provided asswitching elements corresponding to capacitors Cs1, Cs2, and Cs3,respectively.

One electrodes (first electrodes) of the capacitors Cs1, Cs2, and Cs3are connected to the ground via the SW1, SW4, and SW7, respectively. Inaddition, the other electrodes (second electrodes) of the capacitorsCs1, Cs2, and Cs3 are connected to the first electrodes via the SW2 andthe SW3, the SW5 and the SW6, and the SW8 and the SW9, respectively.Further, Vdd (Vdd>ground) is given to a node of the SW2 and the SW3. Anode of the SW5 and the SW6 is connected to the first electrode of thecapacitor Cs1. In addition, a node of the SW8 and the SW9 is connectedto the first electrode of the capacitor Cs2. A voltage of the firstelectrode of the capacitor Cs3 is given to a circuit of a later stage.

Although the description is made citing the storage capacitor of thebooster circuit in this embodiment mode, a storage capacitor to bemanufactured using the present invention is not limited to this but canbe used in other circuits of the semiconductor display device. Inaddition, the semiconductor circuit using the semiconductor circuit asdescribed in this embodiment mode may be formed on a substrate differentform the substrate on which the pixel portion is formed.

Embodiments of the present invention will be hereinafter described.

First Embodiment

In this embodiment, a manufacturing method of a light emitting devicewhich is one of the semiconductor devices of the present invention willbe described. Note that, in this embodiment, a method of manufacturing apixel portion and a storage capacitor included in a circuit providedaround the pixel portion will be described in detail.

First, as shown in FIG. 8A, a base film 5002 including an insulatingfilm such to as a silicon oxide film, a silicon nitride film, or asilicon oxide nitride film is formed on a substrate 5001 including glasssuch as barium borosilicate glass or aluminoborosilicate glassrepresented by #7059 glass, #1737 glass, and the like of CorningCorporation. For example, a silicon oxide nitride film 5002 a producedfrom SiH₄, NH₃, and N₂O is formed with a thickness of 10 to 200 nm(preferably 50 to 100 nm) by the plasma CVD method, and a silicon oxidenitride hydrogenate film 5002 b produced from SiH₄ and N₂O is likewiseformed with a thickness of 50 to 200 nm (preferably 100 to 150 nm) in alaminated shape. Although the base film 5002 is shown as having a twolayer structure in this embodiment, it may be formed as a single layerfilm of the insulating film or a structure in which the insulating filmis laminated in two or more layers.

Island-shaped semiconductor layers 5003 and 5004 are formed of acrystalline semiconductor film which is produced by crystallizing asemiconductor film having an amorphous structure with the lasercrystallization method or the publicly known thermal crystallizationmethod. These island-shaped semiconductor layers 5003 and 5004 areformed with a thickness of 25 to 80 nm (preferably 30 to 60 nm). Amaterial of the crystalline semiconductor film is not limited but ispreferably formed of silicon, silicon germanium (SiGe), or the like.

In order to produce the crystalline semiconductor film with the lasercrystallization method, an excimer laser, a YAG laser, or a YVO₄ laserof a pulse oscillation type or a continuous light emitting type is used.In the case in which these lasers are used, it is favorable to use amethod of condensing laser beams, which are radiated from a laseroscillator irradiating, in a linear shape and irradiating the laserbeams on a semiconductor film. Although conditions of crystallizationare appropriately selected by an operator, in the case in which theexcimer laser is used, it is favorable to set a pulse oscillationfrequency to 300 Hz and a laser energy density to 100 400 mJ/cm²(representatively, 200 to 300 mJ/cm²). In addition, in the case in whichthe YAG laser is used, it is favorable to use a second higher harmonicand set the pulse oscillation frequency to 30 to 300 kHz and the laserenergy density to 300 to 600 mJ/cm² (representatively, 350 to 500mJ/cm²). Then, the laser beams condensed in a linear shape areirradiated over an entire surface of a substrate with a width of 100 to1000 μm, for example, 400 μm. At this point, an overlap ratio of thelinear laser beams is set to 50 to 90%.

Note that not only silicon but also silicon germanium may be used in thesemiconductor film. In the case in which silicon germanium is used, aconcentration of the germanium is preferably about 0.01 to 4.5 atomic %.

Subsequently, a gate insulating film 5007 covering the island-shapedsemiconductor layers 5003 and 5004 is formed. The gate insulating film5007 is formed of an insulating film containing silicon with a thicknessof 40 to 150 nm using the plasma CVD method or the sputtering method. Inthis embodiment, the gate insulating film 5007 is formed of a siliconoxide nitride film with a thickness of 120 nm. It is needless to mentionthat the gate insulating film 5007 is not limited to such a siliconoxide nitride film and an insulating film containing other silicon maybe used in a single layer or a laminated layer structure. For example,in the case in which a silicon oxide film is used, the silicon oxidefilm is formed by mixing TEOS (Tetraethyl Orthosilicate) and O₂ with theplasma CVD method, setting a reactive pressure and a substratetemperature thereof to 40 Pa and 300 to 400° C., respectively, anddischarging the mixed TEOS and O₂ at a high frequency (13.56 MHz), apower flux density of 0.5 to 0.8 W/cm². The silicon oxide film producedin this way can thereafter obtain favorable characteristics as a gateinsulating film through thermal annealing at 400 to 500° C. In addition,aluminum nitride can be used as a gate insulting film. Since thealuminum nitride has relatively high thermal conductivity, heatgenerated by a TFT can be diffused efficiently. Further, after formingsilicon oxide, silicon oxide nitride, or the like which does not containaluminum, a film laminated aluminum nitride thereon may be used as agate insulating film.

Then, a first conductive film 5008 and a second conductive film 5009 forforming a gate electrode on the gate insulating film 5007 are formed. Inthis embodiment, the first conductive film 5008 is formed of Ta with athickness of 50 to 100 nm and the second conductive film 5009 is formedof W with a thickness of 100 to 300 nm.

A Ta film is formed by sputtering a target of Ta with Ar. In this case,if an appropriate amount of Xe or Kr is added to Ar, an internal stressof the Ta film can be eased to prevent exfoliation of the film. Inaddition, a Ta film of an α phase has a resistivity of approximately 20μΩcm and can be used for a gate electrode, but a Ta film of a β phasehas a resistivity of approximately 180 μΩcm and is not suitable to useas a gate electrode. In order to form the Ta film of the α phase, iftantalum nitride having a crystal structure close to the α phase of Tais formed as a base of Ta with a thickness of approximately 10 to 50 nm,the Ta film of the α phase can be obtained easily.

In the case in which a W film is formed, it is formed by the sputteringmethod targeting W. Besides, the W film can also be formed by thermalCVD method using tungsten hexafluoride (WF₆). In any case, it isnecessary to realize a low resistivity in order to use the W film as agate electrode, and it is desirable to set a resistivity of the W filmto 20 μΩcm or less. Reduction of a resistivity can be realized in the Wfilm by increasing a size of a crystal grain. However, in the case inwhich a large quantity of impurity components such as oxygen arecontained in W, crystallization is hindered and a resistivity of the Wfilm is increased. Consequently, in the case in which the W film isformed by the sputtering method, the W film is formed using a W targetwith a purity of 99.99 or 99.9999% and giving careful consideration suchthat impurities are not mixed from a chemical vapor at the time of filmformation, whereby a resistivity of 9 to 20 μΩcm can be realized.

Note that, although the first conductive film 5008 is assumed to be Taand the second conductive film 5009 is assumed to be W, both theconductive films are not specifically limited but may be formed of anelement selected out of Ta, W, Ti, Mo, Al, and Cu, or an alloy materialor a compound material containing the element as a main component. Inaddition, a semiconductor film represented by a polysilicon film dopedwith an impurity element such as phosphorus may be used. As examples ofa combination other than this embodiment, a combination of the firstconductive film formed of tantalum nitride (TaN) and the secondconductive film formed of W, a combination of the first conductive filmformed of tantalum nitride (TaN) and the second conductive film formedof Al, and a combination of the first conductive film formed of tantalumnitride (TaN) and the second conductive film formed of Cu arepreferable. In addition, a semiconductor film represented by apolysilicon film doped with an impurity element such as phosphorus or anAgPdCu alloy may be used as the first conductive film and the secondconductive film.

In addition, the gate electrode is not limited to the two-layerstructure but may be a three-layer structure of, for example, a tungstenfilm, a film of an alloy of aluminum and silicon (Al—Si), and a titaniumnitride film laminated one after another. Further, in the case in whichthe gate electrode is formed in the three-layer structure, tungstennitride may be used instead of tungsten, a film of an alloy of aluminumand titanium (Al—Ti) may be used instead of the film of the alloy ofaluminum and silicon (Al—Si), and a titanium film may be used instead ofthe titanium nitride film.

Note that it is important to appropriately select an optimum etchingmethod or a type of an etchant depending upon materials of conductivefilms.

Next, a mask 5010 with resist is formed, and first etching treatment isperformed in order to form an electrode and a wiring. In thisembodiment, the first etching treatment is performed by using an ICP(Inductively Coupled Plasma) etching method, mixing CF₄ and Cl₂ in a gasfor etching, and inputting an RF (13.56 MHz) power of 500 W in anelectrode of a coil type at a pressure of 1 Pa to generate plasma. An RF(13.56 MHz) power of 100 W is also inputted on the substrate side(sample stage), and a substantially negative self-bias voltage isapplied thereto. In the case in which CF₄ and Cl₂ are mixed, both of theW film and the Ta film are etched to the same degree.

With the above-mentioned etching conditions, ends of the firstconductive film and the second conductive film are formed in a tapershape according to an effect of the bias voltage applied to thesubstrate side by making a shape of the mask with resist suitable. Anangle of the taper portion becomes 15 to 45°. In order to etch a gateinsulating without leaving a residuum on the gate insulating film, it isfavorable to increase etching time at a rate of approximately 10 to 20%.Since a selection ratio of a silicon oxide nitride film with respect tothe W film is 2 to 4 (representatively, 3), a surface where the siliconoxide nitride film is exposed is etched by approximately 20 to 50 nm byover etching treatment. In this way, conductive layers of a first shape5011 to 5014 (first conductive layers 5011 a to 5014 a and secondconductive layers 5011 b to 5014 b) consisting of the first conductivelayer and the second conductive layer are formed by the first etchingtreatment. At this point, in the gate insulating film 5007, a region notcovered by the conductive layers of the first shape 5011 to 5014 isetched by approximately 20 to 50 nm, and a thinned region is formed(FIG. 8B).

Then, first doping treatment is performed to add an impurity element forgiving an N type is added (FIG. 8C). A method of doping may be an iondope method or an ion implantation method. As conditions of the ion dopemethod, a doze quantity is set to 1×10¹³ to 5×10¹⁴ atoms/cm², and anacceleration voltage is set to 60 to 100 keV. As the impurity elementgiving the N type, an element belonging to the XV group, typically,phosphorus (P) or arsenic (As) is used. In this embodiment, phosphorus(P) is used. In this case, the conductive layers 5011 to 5013 becomes amask against the impurity element giving the N type, and first impurityregions 5017 to 5021 are formed in a self-aligning manner. The impurityelement giving the N type is added to the first impurity regions 5017 to5021 in a concentration range of 1×10²⁰ to 1×10²¹ atoms/cm³.

Next, second etching treatment is performed as shown in FIG. 9A.Similarly, the second etching treatment is performed by using the ICP(Inductively Coupled Plasma) etching method, mixing CF₄ and Cl₂ in anetching gas, and inputting an RF (13.56 MHz) power of 500 W in anelectrode of a coil type at a pressure of 1 Pa to generate plasma. An RF(13.56 MHz) power of 50 W is inputted on the substrate side (samplestage), and a self-bias voltage lower than that in the first etchingtreatment is applied thereto. The W film is subjected to the anisotropicetching under such conditions and Ta which is the first conductive filmis subjected to the anisotropic etching at an etching speed, which isslower than that for etching the W film, to form conductive layers of asecond shape 5026 to 5029 (first conductive layers 5026 a to 5029 a andsecond conductive layers 5026 b to 5029 b). At this point, in the gateinsulating film 5007, a region not covered by the conductive layers ofthe second shape 5026 to 5029 are further etched by approximately 20 to50 nm and a thinned region is formed.

An etching reaction of the W film and the Ta film due to the mixed gasof CF₄ and Cl₂ can be surmised from a radical or an ion type to begenerated and a vapor pressure of a reaction product. Comparing vaporpressures of fluorides and chlorides of W and Ta are compared, WF₆ whichis a fluoride of W has an extremely high vapor pressure and the otherfluorides and chlorides WCl₅, TaF₅, and TaCl₅ have similar vaporpressures of the same degree. Therefore, both of the W film and the Tafilm are etched with the mixed gas of CF₄ and Cl₂. However, when anappropriate quantity of O₂ is added to this mixed gas, CF₄ and O₂ reactwith each other to change to CO and F, and a large quantity of an Fradical or an F ion is generated. As a result, an etching speed of the Wfilm having a high vapor pressure of a fluoride increases. On the otherhand, Ta has relatively little increase in an etching speed even if Fincreases. In addition, since Ta is more likely to be oxidized comparedwith W, a surface of Ta is oxidized by adding O₂. Since an oxide of Tadoes not react with fluorine or chlorine, the etching speed of the Tafilm further decreases. Therefore, it becomes possible to differentiateetching speeds of the W film and the Ta film and to make the etchingspeed of the W film higher than that of the Ta film.

Then, as shown in FIG. 9B, second doping treatment is performed. In thiscase, an impurity element giving the N type is doped with conditionsthat a doze quantity is decreased to be lower than that in the firstdoping treatment and an acceleration is increased to be higher than thatin the first doping treatment. For example, the second doping treatmentis performed with the acceleration voltage of 70 to 120 keV and the dozequantity of 1×10¹³ atoms/cm² to form a new impurity region on the innerside of the first impurity regions which are formed in the island-shapedsemiconductor layer in FIG. 8C. The doping is performed such that theimpurity element is also added to a region on the lower side of thesecond conductive layers 5026 a to 5028 a using the conductive layers ofthe second shape 5026 and 5028 as a mask against the impurity element.In this way, third impurity regions 5032 to 5037 overlapping the secondconductive layers 5026 a to 5028 a and second impurity regions 5042 to5047 between the first impurity regions and the third impurity regions.The impurity element giving the N type is adapted to have aconcentration of 1×10¹⁷ to 1×10¹⁹ atoms/cm³ in the second impurityregions and 1×10¹⁶ to 1×10¹⁸ atoms/cm³ in the third impurity regions.

Then, as shown in FIG. 9C, fourth impurity regions 5052 to 5057 of anopposite conductive type of the first conductive type are formed in theisland-shaped is semiconductor layer 5004 forming the p-channel TFT. Theimpurity regions are formed in a self-aligning manner using the secondconductive layer 5028 b as a mask against an impurity element. At thispoint, the island-shaped semiconductor layer 5003 and the firstelectrode for capacitor 5029 forming the n-channel TFT are coatedentirely with a resist mask 5200. Although phosphorus is added atdifferent concentrations in the respective impurity regions 5052 to5057, the impurity regions are formed by an ion dope method usingdiborane (B₂H₆) and are adapted to have an impurity concentration of2×10²⁰ to 2×10²¹ atoms/cm³ in any region.

The impurity regions are formed in the respective island-shapedsemiconductor layers in the above-mentioned process. The secondconductive layers 5026 to 5028 overlapping the island-shapedsemiconductor layers function as the gate electrode. In addition, thesecond conductive layer 5029 functions as the first electrode forcapacitor.

Then, with an object of conductive type control, a process foractivating the impurity elements added to the respective island-shapedsemiconductor layer is performed. This process is performed by a thermalanneal method using an anneal furnace. Besides, an laser anneal methodor a rapid thermal anneal method (RTA method) can be applied. In thethermal anneal method, the process is performed in a nitrogen atmospherewith an oxygen concentration of 1 ppm or less, preferably 0.1 ppm orless, at a temperature of 400 to 700° C., representatively, 500 to 600°C. In this embodiment, heat treatment is performed at 500° C. for fourhours. However, in the case in which the wiring material used in thesecond conductive layers 5026 to 5029 is susceptible to heat, it ispreferable to form an interlayer insulating film (containing silicon asa main component) in order to protect the wiring and the like and, then,activate the film.

Moreover, a process for performing heat treatment at a temperature of300 to 450° C. for 1 to 12 hours in an atmosphere containing 3 to 100%of nitrogen to hydrogenate the island-shaped semiconductor layer isperformed. This process is a process for terminating dangling bond of asemiconductor layer with thermally excited hydrogen. As other means ofhydrogenation, plasma hydrogenation (using hydrogen excited by plasma)may be performed.

Subsequently, as shown in FIG. 10A, a first inorganic insulating film5060 consisting of silicon oxide nitride with a thickness of 10 to 200nm is formed using the CVD method. Note that the first inorganicinsulating film is not limited to a silicon oxide nitride film, and anyinorganic insulating film containing nitrogen may be used as the firstinorganic insulating film as long as the film can suppress penetrationof moisture to and from an organic resin film to be formed later. Forexample, silicon nitride, aluminum nitride, or aluminum oxide nitridecan be used.

Note that aluminum nitride has a relatively high thermal conductivityand can effectively diffuse heat generated in a TFT or a light emittingelement.

Next, an organic resin film 5061 consisting of a positive photosensitiveorganic resin is formed on the first inorganic insulating film 5060.Although the organic resin film 5061 is formed using positivephotosensitive acrylic in this embodiment, the present invention is notlimited to this.

In this embodiment, the organic resin film 5061 is formed by applyingpositive photosensitive acrylic with a spin coat method and baking thesame. Note that a film thickness of the organic resin film 5061 is setto be approximately 0.7 to 5 μm (preferably, 2 to 4 μm) after baking.

Next, a part where an opening part is desired to be formed is exposed tolight using a photo mask. Then, after developing the part with adeveloper containing TMAH (tetramethyl ammonium hydroxide) as a maincomponent, the substrate is dries, and baking is performed at 220° forapproximately one hour. Then, as shown in FIG. 10B, the opening part isformed in the organic resin film 5061, and a part of the first inorganicinsulating film 5060 is exposed in the opening part.

Note that, since the positive photosensitive acrylic is light brown, itis subjected to decolorizing treatment when light emitted from a lightemitting element travels to the substrate side. In this case, beforebaking, the entire photosensitive acrylic after development is exposedto light again. In the exposure at this point, slightly stronger lightis irradiate compared with the exposure for forming the opening part orirradiation time is extended such that the exposure can be performedcompletely. For example, when a positive acrylic resin with a filmthickness of 2 μm is decolorized, in the case in which anonmagnification projection aligner (more specifically, MPA manufacturedby Canon Inc.) utilizing multi-wavelength light consisting of a g ray(436 nm), an h ray (405 nm), and an i ray (365 nm) which are spectrumlight of an ultrahigh pressure mercury vapor lamp is used, the light isirradiated for approximately 60 sec. The positive acrylic resin iscompletely decolorized by this exposure.

In addition, although baking is performed at the temperature of 220° C.after development in this embodiment, baking may be performed at a hightemperature of 220° C. after performing baking at a low temperature of100° C. as pre-baling after development.

Then, as shown in FIG. 10C, covering the opening part in which a part ofthe first inorganic insulating film 5060 is exposed and the organicresin film 5061, a second inorganic insulating film 5062 consisting ofsilicon nitride is formed using an RF sputtering method. A filmthickness of the second inorganic insulating film 5062 is desirablyapproximately 10 to 200 nm. In addition, the second inorganic insulatingfilm is not limited to a silicon oxide nitride film, and any inorganicinsulating film containing nitrogen may be used as the second inorganicinsulating film as long as the film can suppress penetration of moistureto and from the organic resin film 5061. For example, silicon nitride,aluminum nitride, or aluminum oxide nitride can be used.

Note that in a silicon oxide nitride film or an aluminum oxide nitridefilm, a ratio of atomic % of oxygen and nitrogen thereof relates to abarrier property of the same. The higher the ratio of nitrogen tooxygen, the higher the barrier property. In addition, more specifically,a ratio of nitrogen is desirably higher than a ratio of oxygen.

In addition, a film formed using the RF sputtering method is high indenseness and excellent in the barrier property. As conditions of the RFsputtering, for example, in the case in which a silicon oxide nitridefilm is formed, with an Si target, gases of N₂, Ar, and N₂O are flownsuch that a flow ratio thereof becomes 31:5:4, and the film is formedwith a pressure of 0.4 Pa and an electric power of 3000 W. In addition,for example, in the case in which a silicon nitride film is formed, withan Si target, gases of N² and Ar are flown such that a flow ratio in achamber of becomes 20:20, and the film is formed with a pressure of 0.8Pa, an electric power of 3000 W, and a film formation temperature of215° C.

A first interlayer insulating film is formed of this organic resin film5061, the first inorganic insulating film 5060, and the second inorganicinsulating film 5062.

Next, as shown in FIG. 11A, in the opening part of the organic resinfilm 5061, a contact hole is formed in the gate insulating film 5007,the first inorganic insulating film 5060, and the second inorganicinsulating film 5062 using the dry etching method.

By the opening of this contact hole, a part of the first impurityregions 5017 and 5019 and the fourth impurity regions 5052 and 5057 areexposed. Conditions of this dry etching are appropriately set accordingto materials of the gate insulating film 5007, the first inorganicinsulating film 5060, and the second inorganic insulating film 5062. Inthis embodiment, since silicon oxide is used for the gate insulatingfilm 5007, silicon oxide nitride is used for the first inorganicinsulating film 5060, and silicon nitride is used for the secondinorganic insulating film 5062, first, the second inorganic insulatingfilm 5062 consisting of silicon nitride and the first inorganicinsulating film 5060 consisting of silicon oxide nitride are etchedusing CF₄, O₂, and He as etching gases. Thereafter, the gate insulatingfilm 5007 consisting of silicon oxide is etched using CHF₃.

Note that, at the time of this dry etching, since the first inorganicinsulating film 5060 and the second inorganic insulating film 5062 onthe first electrode for capacitor 5029 are used as a dielectric body ofa storage capacitor, the films are protected by a resist mask or thelike so as not to be etched.

In addition, it is essential to prevent the organic resin film 5061 frombeing exposed in the contact hole at the time of etching.

Next, a conductive film is formed on the second inorganic insulatingfilm 5062 so as to cover the contact hole and patterned, whereby wirings5064 to 5067 connected to the first impurity regions 5017 and 5019 andthe fourth impurity regions 5052 and 5057, a wiring for leading 5068 tobe electrically connected to an external terminal, and a secondelectrode for capacitor 5069 are formed. Note that a storage capacitor5070 is formed in a part where the second electrode for capacitor 5069and the first electrode for capacitor 5029 overlap each other with thefirst inorganic insulating film 5060 and the second inorganic insulatingfilm 5062 between them in the opening part of the organic resin film5061.

Note that, in this embodiment, the wirings 5064 to 5067, the wiring forleasing 5068, and the second electrode for capacitor 5069 are formed ofthe conductive film with the three layer structure in which a Ti filmwith a thickness of 100 nm, an Al film with a thickness of 300 nm, and aTi film with a thickness of 150 nm are continuously formed by thesputtering method on the second inorganic insulating film 5062. However,the present invention is not limited to this structure. These may beformed of a conductive film with a single layer or may be formed of aconductive film with plural layers other than three layers. In addition,a material is not limited to this.

For example, these may be formed using a conductive film in which an Alfilm containing Ti is laminated after forming the Ti film or may beformed using a conductive film in which an Al film containing W islaminated after forming the Ti film.

Next, a pixel electrode 5072 being in contact with the wiring 5067 isformed by forming a transparent conductive film, for example, an ITOfilm with a thickness of 110 nm and patterning the same. The pixelelectrode 5072 is arranged so as to be in contact with and overlap thewiring 5067, whereby contact between them is realized. In addition, atransparent conductive film containing indium oxide mixed with 2 to 20%of zinc oxide (ZnO) may be used. This pixel electrode 5072 becomes ananode of the light emitting element (FIG. 11B).

Next, a photosensitive organic resin of a negative type or a positivetype is formed and a part desired to be opened is exposed to light,whereby a second interlayer insulating film 5073 having an opening partis formed. Note that, a part of the pixel electrode 5072 and a part ofthe wiring for leading 5068 are exposed by this process.

Since roundness can be given to a section of the opening part by usingthe photosensitive organic resin, coverage of an electroluminescencelayer an a cathode which are formed later can be made satisfactory, anda defect called shrink in which a light emitting area decreases can bereduced.

Then, a third interlayer insulating film 5074 consisting of siliconnitride is formed on the second interlayer insulating film 5073 usingthe RF sputtering method so as to cover the exposed parts of the pixelelectrode 5072 and the wiring for leading 5068. Note that the thirdinterlayer insulating film 5074 is not limited to silicon nitride, andany inorganic insulating film containing nitrogen may be used as long aspenetration of moisture to and from the second interlayer insulatingfilm 5073 can be suppressed. For example, silicon nitride, aluminumnitride, or aluminum nitride oxide can be used.

Then, by patterning the third interlayer insulating film 5074, a part ofthe pixel electrode 5072 and a part of the wiring for leading 5068 areexposed in the opening part of the second interlayer insulating film5073.

At the time of this etching, it is essential to make an arrangement suchthat the second interlayer insulating film 5073 is not exposed in thecontact hole.

Next, the electroluminescence layer 5075 is formed by the evaporationmethod and a cathode (MgAg electrode) 5076 is further formed by theevaporation method. At this point, it is desirable to apply heattreatment to the pixel electrode 5072 prior to forming theelectroluminescence layer 5075 and the cathode 5076 and completelyremove moisture. Note that, although the MgAg electrode is used as acathode of the OLED in this embodiment, other publicly known materialsmay be used as long as it forms a conductive film with a small workfunction. For example, Ca, Al, CaF, MgAg, or AlLi may be used.

Note that AlLi is used as a cathode, Li in AlLi can be prevented fromentering the substrate side of the third interlayer insulating film 5074by the third interlayer insulating film 5074 containing nitrogen.

Here, data indicating a blocking effect of a silicon nitride film, whichis formed by the sputtering method with high frequency discharge,against lithium is shown in FIGS. 25A and 25B. FIG. 25A shows a C-Vcharacteristic of an MOS structure with a silicon nitride film formed bythe sputtering method with the high frequency discharge (represented asRF-SP SiN) as a dielectric body. Note that “Li-dip” means a solutioncontaining lithium was spin-coated on the silicon nitride film, whichmeans that the silicon nitride film was intentionally contaminated bylithium for an experiment. In addition, FIG. 25B shows a C-Vcharacteristic of an MOS structure with a silicon nitride film formed bythe plasma CVD method (represented as CVD SiN) as a dielectric body forcomparison purpose. Note that, in data of FIG. 25B, an alloy film inwhich lithium is added to aluminum as a metal electrode is used. As aresult of applying a usual BT experiment to these films (morespecifically, as shown in FIG. 25A, heating treatment was performed forone hour at a temperature of ±150° C. in addition to voltage applicationof 1.7 MV), whereas almost no change was observed in the C-Vcharacteristic of the silicon nitride film formed by sputtering methodwith the high frequency discharge, large change was observed in the C-Vcharacteristic of the silicon nitride film formed by the plasma CVDmethod and contamination by lithium was confirmed. These data indicatethat the silicon nitride film formed by the sputtering method with thehigh frequency discharge has a very effective blocking effect againstlithium diffusion.

Note that a publicly known material can be used s theelectroluminescence layer 5075. Although a two layer structureconsisting of a hole transporting layer and an emitting layer isprovided as an electroluminescence layer in this embodiment, any one ofa hole injection layer, an electron injection layer, and an electrontransporting layer may be provided. In this way, various examples havebeen reported concerning a combination, and any structure of theexamples may be used.

For example, SAlq, CAlq, and the like may be used as the electrontransporting layer or the hole blocking layer.

Note that it is sufficient that a film thickness of theelectroluminescence layer 5075 is 10 to 400 nm (typically 60 to 150 nm)and a thickness of the cathode 5076 is 80 to 200 nm (typically, 100 to150 nm).

In this way, a light emitting device with a structure as shown in FIG.12A is completed. In FIG. 12A, reference numeral 5081 denotes a pixelportion and 5082 denotes a drive circuit or other circuits. Note that apart where the pixel electrode 5072, the electroluminescence layer 5075,and the cathode 5076 overlap each other is equivalent to the OLED.

In addition, a part of the cathode 5076 is connected to the wiring forleading 5068. The wiring for leading 5068 is electrically connected to aterminal to be connected to the FPC. A sectional structure of the partto be connected to the FPC (FPC connection part) 5083 is shown in FIG.12B.

An electrode for FPC 5085 formed from the same conductive layer as thegate electrode is formed on the gate insulating film 5007. Then, theelectrode for FPC 5085 is connected to the wiring for leading 5068 via acontact hole 5086 formed in the first inorganic insulating film 5060 andthe second inorganic insulating film 5062 in the opening part of theorganic resin film 5061.

Then, on the electrode for FPC 5085, an opening part of the organicresin film 5061 is provided and the first inorganic insulating film 5060and the second inorganic insulating film 5062 are etched to be removed,whereby the electrode for FPC 5085 is exposed. Thereafter, a terminalfor FPC 5084 formed from the same transparent conductive film as thepixel electrode 5072 is formed on the electrode for FPC 5085.

A terminal of the FPC is connected to the terminal for FPC 5084 via aconductive resin having anisotropy.

Reference numeral 5087 denotes a cover material, which is high in airtightness and is sealed by a sealing material 5088 emitting less gas.Note that, as shown in FIG. 12B, in order to increase adhesion of thecover material 5087 and the element substrate on which the lightemitting element is formed, unevenness may be provided by forming pluralopening parts in the second interlayer insulating film 5073 in a part onwhich the sealing material 5088 is applied.

Note that the structure and the specific producing method of the TFTdescribed in this embodiment are only an example, and the presentinvention is not limited to this structure.

Second Embodiment

In this embodiment, a structure of a light emitting device having asectional structure different from that of the light emitting deviceshown in the first embodiment will be described.

In a light emitting device shown in FIG. 13A, after forming a secondinorganic insulating film 7500, a transparent conductive film is formedand patterned before forming a contact hole, whereby a pixel electrode7501 is formed. Then, a gate insulating film 7502, a first inorganicinsulating film 7503, and the second inorganic insulating film 7500 areetched in an opening part of an organic resin film 7504 to form thecontact hole, and a wiring 7506 electrically connecting a TFT 7505 andthe pixel electrode 7501 is formed.

In this way, by forming the pixel electrode 7501 before forming thewiring 7506, a process of polishing a surface of the pixel electrodebefore forming the wiring 7506 can be provided.

In a light emitting device shown in FIG. 13B, after forming a secondinorganic insulating film 7510, a gate insulating film 7512, a firstinorganic insulating film 7513, and the second inorganic insulating film7510 are etched in an opening part of an organic resin film 7514 to forma contact hole, and a wiring 7516 electrically connecting to a TFT 7515is formed.

Then, a second interlayer insulating film 7517 is formed covering thewiring 7516 and the second inorganic insulating film 7510. The secondinterlayer insulating film 7517 may be a positive photosensitive organicresin film or a negative photosensitive organic resin film. In FIG. 13B,the second interlayer insulating film 7517 is formed using positiveacrylic.

Then, an opening part is formed in the second interlayer insulating film7517 by exposing it to light to expose a part of the wiring 7516.Thereafter, a third interlayer insulating film 7518 is formed on thesecond interlayer insulating film 7517 covering the opening part, and apart of the third interlayer insulating film 7518 is removed in theopening part to expose a part of the wiring 7516. At this point, anarrangement is made such that the second interlayer insulating film 7517is not exposed in the opening part.

Then, a transparent conductive film is formed on the third interlayerinsulating film 7518 and patterned, whereby a pixel electrode 7519connected to the wiring 7516 is formed.

A light emitting device shown in FIG. 13C indicates an example in which,after forming a pixel electrode 7521 on a second inorganic insulatingfilm 7520, a third interlayer insulating film 7522 is formed usingnegative acrylic. In the case in which the third interlayer insulatingfilm 7522 is formed using negative acrylic, it is unnecessary to performexposure with the object of decolorizing the third interlayer insulatingfilm 7522.

FIG. 13D illustrates an example of, in the case in which polythiophene(PEDOT) as a hole injection layer is used in a part of anelectroluminescence layer of a light emitting element, patterning toremove the PEDOT film.

Since the polythiophene (PEDOT) is generally formed as a film using thespin coating method, even a part not desired to be formed as a film isformed as a film. Thus, after forming a PEDOT film 7531 on a pixelelectrode 7530, a light emitting layer 7532 and a cathode 7533 areformed by evaporation using a mask for evaporation. Although aparaphenylenevinylene (PPV) is used as the light emitting layer in thisembodiment, any film may be used as long as it can be formed by theevaporation method. In addition, although Ca is used as the cathode7533, any material may be used as long as it is a material with a smallwork function and can be formed by the evaporation method.

Next, PEDOT is patterned by ashing using oxygen plasma with the cathode7533 as a mask.

Next, an capacitor electrode 7534 is formed. An capacitor electrode isan electrode provided for lowering a resistance of a cathode andconsists of a metal material having a resistance lower than that of thecathode. The capacitor electrode 7534 is obtained by forming aconductive film consisting of the metal material having a resistancelower than that of the cathode and, then, patterning the conductivefilm.

Then, a protective film 7535 electrically connecting the capacitorelectrode 7534 and the cathode 7533 is formed by evaporation using amask for evaporation. The protective film 7535 consists of a metalmaterial, which may be the same as the material for the cathode 7533.

Note that, in FIG. 13D, an example of patterning a hole injection layerwith a cathode of a light emitting element as a mask is shown. However,this embodiment is not limited to this structure. An electroluminescencelayer other than the hole injection layer may be patterned with thecathode as a mask.

In a light emitting device shown in FIG. 14A, after forming a secondinorganic insulating film 7610, a conductive film consisting of a metalmaterial having a resistance lower than that of a cathode is formed andpatterned, whereby an capacitor electrode 7634 is formed. Then, a gateinsulating film 7612, a first inorganic insulating film 7613, and thesecond inorganic insulating film 7610 are etched in an opening part ofan organic resin film 7614 to form a contact hole, and a wiring 7616electrically connecting a TFT 7615 and an capacitor electrode 7634 isformed.

The wiring 7616 is in contact with an electroluminescence layer 7617 ina part thereof and functions as a cathode.

In a light emitting device shown in FIG. 14B, after forming a cathode7700 on a second inorganic insulating film 7701, an electroluminescencelayer 7702 and an ITO film 7703 are formed. At this point, a workfunction can be reduced by adding Li to the ITO film 7703. Then, an ITOfilm 7704 is formed anew separately covering the ITO film 7703 addedwith Li.

Third Embodiment

In this embodiment, electric connection between an capacitor electrodefor lowering a resistance of a cathode and a terminal for FPC to beconnected to a terminal of an FPC will be described.

FIG. 15A shows a sectional view of a light emitting device at a pointwhen, after a third interlayer insulating film 6201 is formed on asecond interlayer insulating film 6200 having an opening part, ancapacitor electrode 6202 is formed on the third interlayer insulatingfilm 6201. The capacitor electrode 6202 is formed of a material having awiring resistance lower than that of a cathode to be formed later.

Note that an electrode for FPC 6204 formed of the same conductive filmas a gate electrode 6203 of a TFT is formed in an opening part of thesecond interlayer insulating film 6200. In addition, a terminal for FPC6205 formed of the same transparent conductive film as a pixel electrode6206 is formed on the electrode for FPC 6204.

At the point of FIG. 15A, the terminal for FPC 6205 is covered by thethird interlayer insulating film 6201 in an FPC connection part 6215.

Next, as shown in FIG. 15B, a part of the third interlayer insulatingfilm 6201 is etched to be removed, whereby the terminal for FPC 6205 andthe pixel electrode 6206 are partly exposed. At this point, the secondinterlayer insulating film 6200 is not to be exposed.

After laminating an electroluminescence layer 6210 and a cathode 6211 onthe pixel electrode 6206, a protective film 6212 electrically connectingthe terminal for FPC 6205 and the cathode 6211 is formed.

In the above-mentioned structure, when the capacitor electrode 6202 isformed by etching, since the pixel electrode is covered by the thirdinterlayer insulating film 6201, the surface of the pixel electrode 6206can be prevented from being roughened by the etching.

FIG. 16 shows a plan view of a substrate (element electrode), on whichlight emitting elements are formed, of the light emitting device of thisembodiment. A state in which a pixel portion 831, scanning line drivecircuits 832, a signal line drive circuit 833, and the terminals for FPC6205 are formed on a substrate 830 is shown. The terminals for FPC 6205and the respective drive circuits, a power supply line and opposedelectrodes formed in the pixel portion are connected by lead wirings835. The light emitting elements are formed the respective adjacentcapacitor electrodes 6202 which are laid out in a stripe shape.

In addition, an IC chip on which a CPU or a memory is formed may beimplemented on an element substrate by a COG (Chip on Glass) method orthe like, if necessary.

Fourth Embodiment

The present invention explains the configuration of the light emittingapparatus having a controller formed on the same substrate of a pixelportion and a driving circuit.

The configuration of the controller of this embodiment is shown in FIG.17. A controller is composed of an interface (I/F) 650, the panel linkreceiver 651, the phase locked loop 652 (PLL), the field programmablelogic device 653 (FPGA), SDRAM (Synchronous Dynamic Random AccessMemory) 654 and 655, ROM (Read Only Memory) 657, the voltage adjustmentcircuit 658, and the power supply 659. In addition, although SDRAM isused in this embodiment, if writing and read-out of high-speed data arepossible instead of SDRAM, it is possible to also use DRAM (DynamicRandom Access Memory) and SRAM (Static Random Access Memory).

In the panel link receiver 651, the digital video signal is carried outparallel-serial conversion and inputted into the semiconductor displaydevice through the interface 650, and it is inputted into the signalconversion portion 653 as a digital video signal corresponding to eachcolor of R, G, and B.

Moreover, based on the various signals inputted into the semiconductordisplay device through the interface 650, a Hsync signal, a Vsyncsignal, the clock signal CLK, and exchange voltage (AC Cont) aregenerated in the panel link receiver 651, and they are inputted into thesignal conversion portion 653.

The phase locked loop 652 has the function to unite the phase of thefrequency of the various signals inputted into a semiconductor displaydevice, and the frequency of the signal conversion portion 653 ofoperation. Although the operation frequency of the signal conversionportion 653 is not necessarily the same as the frequency of the varioussignals inputted into a semiconductor display device, the operationfrequency of the signal conversion portion 653 is adjusted in the phaselocked loop 652 so that it may synchronize mutually.

The program which controls operation of the signal conversion portion653 is memorized in ROM 657, and the signal conversion portion 653operates according to this program.

The digital video signal inputted into the signal conversion portion 653is once written in SDRAMs 654 and 655, and is held. In the signalconversion portion 653, among the digital video signals of all the bitscurrently held at SDRAM 654, every 1 bit of digital video signalscorresponding to all pixels is read, and they are inputted into a signalline driver circuit.

Moreover, in the signal conversion portion 653, the information aboutthe length of the luminescence period of OLED corresponding to each bitis inputted into a scanning line driver circuit.

In addition, the voltage adjustment circuit 658 adjusts the voltagebetween the anode and the cathode of OLED of each pixel synchronizingwith the signal inputted from the signal conversion portion 653. Thepower supply 659 supplies the power-supply voltage of a direct currentto the voltage adjustment circuit 658, the signal line driver circuit660, the scanning line driver circuit 661, and the pixel portion 662.

The capacitance having the configuration shown in the Embodiment Modecan be used for the circuits which can be made from capacitance, forexample, PLL 652, SDRAM 654 and 655, among various kinds of circuitsheld by controller. Moreover, the panel link receiver 651 usescapacitance in some cases, and in that case, capacitance having theconfiguration shown in the Embodiment Mode can be used. Also, thevoltage adjustment circuit 658 can be used if it is a capacitydivisional type.

This embodiment may also be implemented by being freely combined withEmbodiments 1 to 3.

Fifth Embodiment

In this embodiment, a structure of a liquid crystal display device,which is one of the semiconductor display devices of the presentinvention, will be described.

A sectional view of the liquid crystal display device of this embodimentis shown in FIG. 18. In FIG. 18, a TFT 9001 is formed on an insulatingsurface. The TFT 9001 is a top gate type and has a semiconductor film9002, a gate insulating film 9003 which is in contact with thesemiconductor film 9002, and a gate electrode 9004 which is in contactwith the gate insulating film 9003.

On the other hand, a first electrode for capacitor 9007 formed on thegate insulating film 9003 can be formed from the same conductive film asthe gate electrode 9004.

Further, a first inorganic insulating film 9008 is formed so as to coverthe TFT 9001 and the first electrode for capacitor 9007. The firstinorganic insulating film 9008 is an insulating film containing nitrogenand has a characteristic that it is less likely to penetrate moisturethan an organic resin film to be formed later.

Then, after applying a photosensitive organic resin on the firstinorganic insulating film 9008, the photosensitive organic resin isbaked and a part desired to be opened is exposed to light and developed,whereby an organic resin film 9009 having the opening part is formed. Atthis point, a part of the first inorganic resin film 9008 is exposed inthe opening part.

Then, a second inorganic insulating film 9010 is formed covering theorganic resin film 9009 and the part of the first inorganic insulatingfilm 9008 exposed in the opening part. The second inorganic insulatingfilm 9010, like the first inorganic insulating film 9008, is aninsulating film containing nitrogen and has a characteristic that it isless likely to penetrate moisture than an organic resin film to beformed later.

Then, in the opening part of the organic resin film 9009, the gateinsulating film 9003, the first inorganic insulating film 9008, and thesecond inorganic insulating film 9010 are subjected to dry etching suchthat a part of the semiconductor film 9002 is exposed, and a contacthole is formed. The semiconductor film 9002 has an effect as an etchingstopper.

At this point, the first inorganic insulating film 9008 and the secondinorganic insulating film 9010 existing on the first electrode forcapacitor 9007 are covered by a resist mask so as not to be etched.

Then, a conductive film is formed on the second inorganic insulatingfilm 9010 so as to cover the contact hole. Then, the conductive film isetched, whereby wirings 9011 connected to the semiconductor film 9002and a second electrode for capacitor 9012 are formed. The secondelectrode for capacitor 9012 overlaps the first electrode for capacitor9007 with the first inorganic insulating film 9008 and the secondinorganic insulating film 9010 between them. A storage capacitor 9013 isformed of the second electrode for capacitor 9012, the first inorganicinsulating film 9008, the second inorganic insulating film 9010, and thefirst electrode for capacitor 9007.

Then, a transparent conductive film is formed on the second inorganicinsulating film 9010 so as to cover the wirings 9011 and the secondelectrode for capacitor 9012 and patterned, whereby a pixel electrode9015 is formed. The pixel electrode 9015 is connected to one of thewirings 9011 and the second electrode for capacitor 9012.

Then, positive acrylic is applied on the second inorganic insulatingfilm 9010 covering the pixel electrode 9015, the wirings 9011, and thesecond electrode for capacitor 9012 and baked, then partially exposed tolight and developed, whereby a third interlayer insulating film 9017having an opening part is formed. Although positive acrylic is used forthe third interlayer insulating film 9017 in this embodiment, negativeacrylic may be used. The pixel electrode 9015 is exposed in the openingpart. The third interlayer insulating film 9017 is used as a spacer forkeeping an interval among substrates constant. A thickness thereof isdesirably approximately 0.7 μm to several μm, although it depends upon atype of liquid crystal.

Then, an orientation film 9018 is formed. Usually, a polyimide resin isused for an orientation film for a liquid crystal display device. Afterforming the orientation film, rubbing treatment is applied to theorientation film such that liquid crystal molecules are oriented with acertain constant pre-tilt angle.

A light shielding film 9021, an opposed electrode 9022, and anorientation film 9023 are formed on an opposed substrate 9020 on anopposed side. As the light shielding film 9021, a Ti film, a Cr film, anAl film, or the like are formed with a thickness of 150 to 300 nm. Then,the pixel portion, the element substrate on which the drive circuits areformed, and the opposed substrate are stuck together by a seal material9024. A filler (not shown) is mixed in the seal material 9024, and twosubstrates are stuck together with a uniform interval by this filler andthe third interlayer insulating film 9017. Thereafter, liquid crystal9025 is injected between both the substrates. A publicly known liquidcrystal material only has to be used as a liquid crystal material. Forexample, other than TN liquid crystal, no-threshold anti-ferroelectricmixed liquid crystal showing electro-optical response property, withwhich a transmissivity continuously changes with respect to an electricfield, can also be used. Some no-threshold anti-ferroelectric mixedliquid crystal shows a V-shaped electro-optical response property. Inthis way, an active matrix liquid crystal display device shown in FIG.18 is completed.

The liquid crystal display device described in this embodiment is onlyan example of the liquid crystal device of the present invention, andthe present invention is not limited to the structure shown in FIG. 18.

Note that it is possible to combine this embodiment with the first tofourth embodiments freely.

Sixth Embodiment

In this embodiment, a structure of a drive circuit of a liquid crystaldisplay device, which is one of the semiconductor display devices of thepresent invention, will be described.

FIG. 19A is a schematic block diagram of an active matrix liquid crystaldisplay device of this embodiment. Reference numeral 501 denotes asignal line drive circuit; 503, a scanning line drive circuit; and 504,a pixel portion.

The signal line drive circuit 501 has a shift register circuit 501-1, alatch circuit A 501-2, a latch circuit B 501-3, and a D/A conversioncircuit (DAC) 501-5. Besides, the signal line drive circuit 501 has abuffer circuit and a level shift circuit (both of which are not shown).In addition, for convenience of description, a level shift circuit isincluded in the DAC 501-5.

In addition, reference numeral 503 denotes the scanning line drivecircuit, which may have a shift register circuit, a buffer circuit, anda level shifter circuit.

The pixel portion 504 has plural pixels. A TFT serving as a switchingelement is arranged in each pixel. One of a source and a drain of eachpixel TFT is connected to a signal line and the other is connected to apixel electrode. In addition, the gate is electrically connected to thescanning line. Each pixel TFT controls supply of a video signal to thepixel electrode electrically connected to each pixel TFT. The videosignal is supplied to each pixel electrode, a voltage is applied toliquid crystal sandwiched between each pixel electrode and an opposedelectrode to drive the liquid crystal.

First, operations of the signal line drive circuit 501 will bedescribed. In the shift register circuit 501-1, a timing signal forcontrolling timing at which a digital video signal is latched by thelatch circuit A 501-2 is generated based upon an inputted clock signaland a start pulse.

In the latch circuit A 501-2, the digital video signal is latchedsynchronizing with the generated timing signal. When the video signal islatched in all stages of the latch circuit A 501-2, a latch signal issupplied to the latch circuit B 501-3 in accordance with operationtiming of the shift register circuit 501-1. At this instance, thedigital video signal latched by the latch circuit A 501-2 is transmittedto the latch circuit B 501-3 all at once and latched by latch circuitsof all the stages of the latch circuit B 501-3.

In the latch circuit A 501-2 which has completed transmitting thedigital video signal to the latch circuit B 501-3, the digital videosignal is latched sequentially based upon a timing signal from the shiftregister circuit 501-1.

On the other hand, the digital video signal latched in the latch circuitB 501-3 is supplied to the D/A conversion circuit (DAC) 501-5. The DAC501-5 converts the digital video signal into an analog video signal andsupplies the analog signal to each signal line sequentially.

In the scanning line drive circuit 503, a timing signal from a shiftregister (not shown) is supplied to a buffer circuit (not shown) and toa corresponding scanning line. Since gate electrodes of pixel TFTs forone line are connected to the scanning line and all the pixel TFTs forone line have to be turned ON simultaneously, a buffer circuit with alarge current capacity is used for the above-mentioned buffer circuit.

In this way, switching of a corresponding pixel TFT is performed by ascanning signal from the scanning line drive circuit, an analog videosignal (gradation voltage) from the signal line drive circuit issupplied to the pixel TFT to drive liquid crystal molecules.

In the liquid crystal display device of this embodiment, the D/Aconversion circuit 501-5 is a capacity dividing type and has a capacitorof the structure described in the embodiment mode.

FIG. 19B shows a circuit diagram of the D/A conversion circuit 501-5 ofthis embodiment. The DAC shown in FIG. 19B can handle digital data of nbits (D₀ to D_(n-1)). Note that D₀ is assumed to be an LSB and D_(n-1)is assumed to be an MSB.

As shown in FIG. 19B, the DAC of the present invention has n switches(SW₀ to SW_(n-1)) controlled by each bit of the n-bit digital data (D₀to D_(n-1)), capacitors (C, 2C, . . . , 2^(m-1)C, C, 2C, . . . ,2^(n-m-1)C) connected to the respective switches (SW₀ to SW_(n-1)), andtwo reset switches (Res1 and Res2). These capacitors have capacitieswhich are integer times as large as that of a unit capacitor C. Further,these capacitors are formed of the capacitor of the structure shown inthe embodiment mode.

In addition, the DAC of the present invention has a capacitor C whichconnects a circuit portion corresponding to low order m bits and acircuit portion corresponding to high order (n-m) bits. As shown in FIG.19B, one ends of respective capacitors of the circuit portioncorresponding to the low order m bits form a common connection end. Inaddition, one ends of respective capacitors of the circuit portioncorresponding to the high order (n-m) bits form a common connection end.Note that a capacitor C_(L) is a load capacitor of a signal lineconnected to an output V_(out). In addition, a ground power supply isassumed to be V_(G). Note that V_(G) may be an arbitrary constant powersupply.

A power supply V_(H), a power supply V_(L), an offset power supplyV_(B), and a power supply V_(A) are connected to the DAC of the presentinvention. Analog signals of opposite phases are outputted to the outputV_(out) in the case of V_(H)>V_(L) and the case of H_(V)<V_(L). Notethat, here, the output in the case of V_(H)>V_(L) is assumed to be anormal phase and the case of H_(V)<V_(L) is assumed to be an inversedphase.

The switches (SW₀ to SW_(n-1)) are adapted to be connected to the posersupply V_(L) at the time when inputted digital data (D₀ to D_(n-1)) is 0(Lo) and connected to the power supply V_(H) at the time when inputteddata is 1 (Hi). The reset switch Res1 controls charging of electriccharges from V_(B) to the capacitors (C, 2C, . . . , 2^(n-m-1)C)corresponding to the high order (n-m) bits. In addition, the resetswitch Res2 controls charging of electric charges from V_(A) to thecapacitors (C, 2C, . . . , 2^(m-1)C) corresponding to the low order mbits.

Note that one end of the reset switch Res2 may be connected to the powersupply V_(L) such that a voltage from the power supply V_(A) is notperformed.

Note that, although the signal line drive circuit and the scanning linedrive circuit described in this embodiment are used as drive circuits ofa liquid crystal display device, the drive circuits may be used as drivecircuits of a light emitting device or other semiconductor displaydevices.

Seventh Embodiment

The semiconductor display device of the present invention may have a CPUon the same substrate on which a pixel portion is provided.

FIG. 20A shows a structure of a microprocessor 3200 which is an exampleof a semiconductor circuit included in the semiconductor display deviceof the present invention. The microprocessor 3200 is constituted byvarious circuits. In FIG. 20A, the microprocessor 3200 is constituted bya CPU core 3201, a DRAM 3204, a clock controller 3203, a cache memory3202, a cache controller 3205, a serial interface 3206, an I/O port3207, and the like. It is needless to mention that the microprocessorshown in FIG. 20A is a simplified example and an actual microprocessorhas various kinds of structures depending upon applications of the same.

A storage capacitor having the structure described in the embodimentmode can be used for the cache memory 3202 and the DRAM 3204.

In addition, as one of the semiconductor circuits included in thesemiconductor display device of the present invention, an IC with aspecified application like an ASIC (Application Specific IntegratedCircuit).

FIG. 20B shows a conceptual view of a polycell type standard cell whichis one of ASICs. With the polycell type standard cell, it is attemptedto realize short TAT of a layout design by making heights of cellsidentical. The polycell type standard cell shown in FIG. 20B can formthe storage capacitor, which is described in the embodiment mode, in aDRAM.

Note that the ASIC shown in FIG. 20B is only an example of thesemiconductor circuits included in the semiconductor display device ofthe present invention. The present invention is not limited to this.

Eighth Embodiment

The semiconductor display apparatus formed by the present invention canbe applied to various electronics. Examples of the electronics areportable information terminals (electronic books, mobile computers,cellular phones, or the like), video cameras, digital cameras, personalcomputers, TV receivers, cellular phones, projection displayapparatuses, or the like. Specific examples of these electronics areshown in FIGS. 22A to 22H.

FIG. 22A shows a display apparatus, which is composed of a case 2001, asupport base 2002, a display unit 2003, speaker units 2004, a videoinput terminal 2005, etc. The display apparatus of the present inventionis completed by using the semiconductor display apparatus of the presentinvention to the display unit 2003. The display apparatus refers to alldisplay apparatuses for displaying information, including ones forpersonal computers, for TV broadcasting reception, and foradvertisement.

FIG. 22B shows a digital still camera, which is composed of a main body2101, a display unit 2102, an image receiving unit 2103, operation keys2104, an external connection port 2105, a shutter 2106, etc. The digitalstill camera of the present invention is completed by using thesemiconductor display apparatus of the present invention to the displayunit 2102.

FIG. 22C shows a laptop, which is composed of a main body 2201, a case2202, a display unit 2203, a keyboard 2204, an external connection port2205, a pointing mouse 2206, etc. The laptop of the present invention iscompleted by using the semiconductor display apparatus of the presentinvention to the display unit 2203.

FIG. 22D shows a mobile computer, which is composed of a main body 2301,a display unit 2302, a switch 2303, operation keys 2304, an infraredport 2305, etc. The mobile computer of the present invention iscompleted by using the semiconductor display apparatus of the presentinvention to the display unit 2302.

FIG. 22E shows a portable image reproducing apparatus having a recordingmedium (a DVD player, to be specific). The apparatus is composed of amain body 2401, a case 2402, a display unit A 2403, a display unit B2404, a recording medium (DVD or the like), a reading unit 2405,operation keys 2406, speaker units 2407, etc. The display unit A 2403mainly displays image information whereas the display unit B 2404 mainlydisplays text information. Domestic video games and the like are alsoincluded in the image reproducing apparatus having a recording medium.The portable image reproducing apparatus of the present invention iscompleted by using the semiconductor display apparatus of the presentinvention to the display units A 2403 and B 2404.

FIG. 22F shows a goggle type display (head mounted display), which iscomposed of a main body 2501, display units 2502, and arm units 2503.The goggle type display of the present invention is completed by usingthe semiconductor display apparatus of the present invention to thedisplay units 2502.

FIG. 22G shows a video camera, which is composed of a main body 2601, adisplay unit 2602, a case 2603, an external connection port 2604, aremote control receiving unit 2605, an image receiving unit 2606, abattery 2607, an audio input unit 2608, operation keys 2609, eye pieceportion 2610 etc. The video camera of the present invention is completedby using the semiconductor display apparatus of the present invention tothe display unit 2602.

FIG. 22H shows a cellular phone, which is composed of a main body 2701,a case 2702, a display unit 2703, an audio input unit 2704, an audiooutput unit 2705, operation keys 2706, an external connection port 2707,an antenna 2708, etc. The cellular phone of the present invention iscompleted by using the semiconductor display apparatus of the presentinvention to the display unit 2703. In the case that the semiconductordisplay apparatus of the present invention is the light emittingapparatus, the display unit 2703 displays white letters on blackbackground, therefore the cellular phone consumes less power.

As described above, the application range of the present invention is sowide that it is applicable to electronics of any field. This embodimentcan be operated by combining with any configuration shown in Embodiments1 to 7.

Ninth Embodiment

A photograph shown in FIG. 26A is a sectional SEM (scanning typeelectron microscope) photograph in a state in which dry etchingtreatment is applied to a non-photosensitive acrylic film (filmthickness: approximately 1.3 μm) to pattern it. FIG. 26B is a schematicview of FIG. 26A. In the case in which the dry etching treatment isapplied to the non-photosensitive acrylic film as in the past, a curvedsurface is hardly formed in an upper part of the pattern, and an upperend substantially without a curvature radius (R) is obtained. Inaddition, although a taper angle (contact angle) is approximately 63° ina lower part of the pattern, no curved surface is observed in this lowerend either.

Next, a photograph shown in FIG. 27A is a sectional SEM photograph in astate in which exposure and development treatment are applied to apositive photosensitive acrylic film (film thickness: approximately 2.0μm) to pattern it. FIG. 27B is a schematic view of FIG. 27A. A sectionalshape of the positive photosensitive acrylic film has an extremelygentle curved surface after etching treatment with a developer, and acurvature radius (R) changes continuously. In addition, as a contactangle, a value as small as approximately 32 to 33° is obtained. That is,it is just like the shape shown in FIG. 1B. It can be said that it is avery useful shape in producing the thin film transistor and the displaydevice of the present invention. It is needless to mention that,although a value of the contact angle changes depending upon etchingconditions, a film thickness, and the like, it only has to satisfy30°<θ<65° as described above.

Next, a photograph shown in FIG. 28A is a sectional SEM photograph in astate in which exposure and development treatment are applied to anegative photosensitive acrylic film (film thickness: approximately 1.4μm) to pattern it. FIG. 28B is a schematic view of FIG. 28A. A sectionalshape of the negative photosensitive acrylic film has a gentle S-shapedcurved surface after etching treatment with a developer and is curvedwith a certain curvature radius (R) in an upper end of the pattern. Inaddition, as a contact angle, a value of approximately 47° is obtained.In this case, a length of a part of a tail represented by W of FIG. 28Bis a problem. In particular, in a contact hole (opening part) requiringfine machining, if this tail part becomes long, it is likely that astate in which an electrode or a wiring in a lower layer is not exposedin the contact hole occurs, and disconnection due to contact failure isfeared. However, a possibility of such disconnection decreases if thelength (W) of this tail part is 1 μm or less (preferably, a length lessthan a radius of the contact hole).

Next, a photograph shown in FIG. 29A is a sectional SEM photograph in astate in which exposure and development treatment are applied to apositive photosensitive polyimide film (film thickness: approximately1.5 μm) to pattern it. FIG. 29B is a schematic view of FIG. 29A. Asectional shape of the positive photosensitive polyimide film has aslight tail part (represented by a length W) and a curved upper endafter etching treatment with a developer. However, a certain curvatureradius (R) thereof is small.

Observing the above-mentioned sectional shapes, considerations asdescribed blow can be made. After forming a contact hole (opening part),when a metal film to be an electrode or a wiring is formed, thesputtering method, the evaporation method, or the CVD method is used. Itis known that, when material molecules constituting a thin film depositon a surface to be formed, the material molecules move on the surface tofind a stable site, and tend to gather in a part of a shape having anacute angle (shape to be a projected part) like an upper end of thecontact hole. In particular, this tendency is conspicuous in theevaporation method. Thus, when a sectional shape of the opening part isthe shape as shown in FIG. 26A, since the material molecules concentrateon the edge of the opening part, a film thickness increases in that partlocally and a projected part of an eave shape is formed. This projectedpart is not preferable because it becomes a cause of a failure such asdisconnection (step breakage) later. Therefore, it can be said that thenon-photosensitive acrylic film shown in FIG. 26A and the positivephotosensitive polyimide film shown in FIG. 29A are materialsdisadvantageous from the viewpoint of a coverage.

In addition, in the shape with the tail part formed in the lower end ofthe contact hole as shown in FIGS. 28A and 29A, it is likely that thetail part may cover the bottom surface of the contact hole to causeconnection failure. Therefore, it can be said that the films having sucha shape is a material disadvantageous from the viewpoint of a contactproperty. It is needless to mention that there is no problem if thelength of the tail part is 1 μm or less (preferably, a length less thanthe radius of the contact hole).

By covering an inorganic insulating film with an organic resin film,roughening of a surface due to dry etching can be suppressed. Thus,since it is possible to prevent unevenness from appearing on a surfaceof a pixel electrode or the like to be formed later or a thickness ofthe pixel electrode from becoming irregular, occurrence of displayirregularity can be prevented.

In addition, by covering an organic resin film with an inorganicinsulating film containing nitrogen that is less likely to transmitmoisture compared with the organic resin film, discharge of moisturefrom the organic resin film can be suppressed and, conversely, theorganic resin film is prevented from absorbing moisture to swell. Thus,a wiring can be prevented from corroding due to the moisture dischargedfrom the organic resin film. Moreover, in the case of a light emittingdevice using a light emitting element represented by an organic lightemitting diode (OLED), luminance of the light emitting element can beprevented from deteriorating due to the moisture discharged from theorganic resin film.

Further, by covering an entire organic resin film with an inorganicinsulating film such that the organic resin film is not exposed, theorganic resin film can be prevented from absorbing moisture in analkaline solution to be used at the time of development to swell, andtreatment time of heating treatment with an object of removing themoisture after development can be controlled. Moreover, the moisture inthe organic resin film can be prevented from being discharged to a filmor an electrode adjacent to the organic resin film, and long-termreliability of a panel can be increased.

In addition, in the case in which a non-photosensitive organic resin isused, dry etching is generally used in order to form an opening in aninterlayer insulating film. The dry etching is an etching method usingan active radical or plasma of a reactive gas. Since the interlayerinsulating film has a thickness approximately ten times as large as thatof a gate insulating film, the dry etching with an object of openingtakes time. If time during which a substrate with a TFT formed thereonis exposed to plasma is long, a threshold value of the TFT tends tofluctuate to a positive side due to a so-called charging damage in whicha hole is trapped by the gate insulating film. Thus, by forming anopening with wet etching using a photosensitive organic resin as in thepresent invention, time during which the dry etching is used can bereduced significantly, and fluctuation of the threshold value of the TFTcan be suppressed.

What is claimed is:
 1. A display device comprising: a thin filmtransistor comprising a gate electrode; a conductive layer comprising asame material as the gate electrode; a first insulating film over theconductive layer; an organic resin film over the first insulating film,wherein the organic resin film has an opening, wherein the opening isprovided over the conductive layer; and a second insulating film overthe organic resin film, wherein the second insulating film is in contactwith the first insulating film in the opening.